Treatment of ozonated water in biofilters containing different media

Four parallel biofilters were tested for treatment of ozonated humic water. Two of them contained Kaldnes plastic cylinders (KMT media), one marble an d one expanded clay aggregates (Filtralite NC) as biofilm media. Dual-media filter was used for removal of bacteria from biofilter effluents. After fo ur months of operation, average TOC removal was 37-38% and CODMn removal wa s 43-45% in the ozonation/biofiltration process. Ozonation removed 83% of c olour from the raw water. Over 83% removal of ozonation by-products (aldehy des and ketoacids) was also achieved. Biofiltration increased the levels of heterotrophic bacteria in the water but they were reduced by 88% in the du al media filter. The biofilter media did not have significant effect on tre atment efficiency at the empty bed contact time of 30-40 min.